I'm going to be controversial and say that if sorting by date isn't the default in an email client, it's a broken client.

That's beyond just breaking "Have sensible defaults", and is well into, "Your defaults are broken".

That's the default.

But it sounds like OPs mails were sorted differently for an unknown reason.

lol seriously, my guy didn't even wait until imap was done. what vendetta does he have against Thunderbird

Probably the same vendetta they I have against Windows. Every time I try it, I find it so frustrating. So every time I try, I afford it less and less patience.